diff options
| author | Brandon Philips <brandon@ifup.org> | 2008-11-06 11:19:11 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2008-11-13 14:45:02 -0800 |
| commit | ad0b65efd12d020b046cde8d6f474e37bb98dd73 (patch) | |
| tree | 4006e270b2374817855c844c48cb4b7ed891ab35 | |
| parent | 881e3c9867c585e632dfa4ccb0848b62debc64c7 (diff) | |
USB: cdc-acm.c: fix recursive lock in acm_start_wb error path
Fixes an obvious bug in cdc-acm by avoiding a recursive lock on
acm_start_wb()'s error path. Should apply towards 2.6.27 stable and
2.6.28.
=============================================
[ INFO: possible recursive locking detected ]
2.6.27-2-pae #109
---------------------------------------------
python/31449 is trying to acquire lock:
(&acm->write_lock){++..}, at: [<f89a0348>] acm_start_wb+0x5c/0x7b [cdc_acm]
but task is already holding lock:
(&acm->write_lock){++..}, at: [<f89a04fb>] acm_tty_write+0xe1/0x167 [cdc_acm]
other info that might help us debug this:
2 locks held by python/31449:
#0: (&tty->atomic_write_lock){--..}, at: [<c0260fae>] tty_write_lock+0x14/0x3b
#1: (&acm->write_lock){++..}, at: [<f89a04fb>] acm_tty_write+0xe1/0x167 [cdc_acm]
stack backtrace:
Pid: 31449, comm: python Not tainted 2.6.27-2-pae #109
[<c030f42f>] ? printk+0xf/0x18
[<c0149f33>] __lock_acquire+0xc7b/0x1316
[<c014a63e>] lock_acquire+0x70/0x97
[<f89a0348>] ? acm_start_wb+0x5c/0x7b [cdc_acm]
[<c0312109>] _spin_lock_irqsave+0x37/0x47
[<f89a0348>] ? acm_start_wb+0x5c/0x7b [cdc_acm]
[<f89a0348>] acm_start_wb+0x5c/0x7b [cdc_acm]
[<f89a055d>] acm_tty_write+0x143/0x167 [cdc_acm]
[<c0262a98>] write_chan+0x1cd/0x297
[<c012527e>] ? default_wake_function+0x0/0xd
[<c026111e>] tty_write+0x149/0x1b9
[<c02628cb>] ? write_chan+0x0/0x297
[<c01912c5>] ? rw_verify_area+0x76/0x98
[<c0260fd5>] ? tty_write+0x0/0x1b9
[<c01919ba>] vfs_write+0x8c/0x136
[<c0191afd>] sys_write+0x3b/0x60
[<c0103beb>] sysenter_do_call+0x12/0x3f
=======================
Signed-off-by: Brandon Philips <bphilips@suse.de>
Cc: Oliver Neukum <oliver@neukum.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | drivers/usb/class/cdc-acm.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 20104443081a..d50a99f70aee 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -158,16 +158,12 @@ static int acm_wb_is_avail(struct acm *acm) } /* - * Finish write. + * Finish write. Caller must hold acm->write_lock */ static void acm_write_done(struct acm *acm, struct acm_wb *wb) { - unsigned long flags; - - spin_lock_irqsave(&acm->write_lock, flags); wb->use = 0; acm->transmitting--; - spin_unlock_irqrestore(&acm->write_lock, flags); } /* @@ -482,6 +478,7 @@ static void acm_write_bulk(struct urb *urb) { struct acm_wb *wb = urb->context; struct acm *acm = wb->instance; + unsigned long flags; if (verbose || urb->status || (urb->actual_length != urb->transfer_buffer_length)) @@ -490,7 +487,9 @@ static void acm_write_bulk(struct urb *urb) urb->transfer_buffer_length, urb->status); + spin_lock_irqsave(&acm->write_lock, flags); acm_write_done(acm, wb); + spin_unlock_irqrestore(&acm->write_lock, flags); if (ACM_READY(acm)) schedule_work(&acm->work); else |